Solution 06 is quite good (maybe perfect) from the perspective of binary compatibility. For a while I thought I am going to give up, however then I noticed that there is an added overloaded method. With proper parameters this can cause the previously OK source to become uncompilable.

# location to root of the repository with apifest projects

apifest=${ant.file.common}/../../

# and where is junit?

junit.jar=${apifest}/libs/junit-4.4.jar